8,140 research outputs found
Inelastic contribution of the resistivity in the hidden order in URu2Si2
In the hidden order of URu2Si2 the resistivity at very low temperature shows
no T^2 behavior above the transition to superconductivity. However, when
entering the antiferromagnetic phase, the Fermi liquid behavior is recovered.
We discuss the change of the inelastic term when entering the AF phase with
pressure considering the temperature dependence of the Grueneisen parameter at
ambient pressure and the influence of superconductivity by an extrapolation of
high field data.Comment: 5 pages, 2 figures, SCES conference proceedin
Anomalous broadening of the spin-flop transition in the reentrant spin-glass phase of LaSrCuO ()
The magnetization in a lightly doped LaSrCuO ()
single crystal was measured. Spin-flop transition was clearly observed in the
hole doped antiferromagnetically ordered state under increasing magnetic fields
perpendicular to the CuO plane. In the spin-glass phase below 25K, the
spin-flop transition becomes broad but the step in the magnetization curve
associated with the transition remains finite at the lowest temperature. We
show in this report that, at low temperature, the homogeneous antiferromagnetic
order is disturbed by the re-distribution of holes, and that the spatial
variance of the local hole concentration around increases.Comment: to be published to Physical Review
Constraint on the heavy sterile neutrino mixing angles in the SO(10) model with double see-saw mechanism
Constraints on the heavy sterile neutrino mixing angles are studied in the
framework of a minimal supersymmetric model with {\it double
see-saw mechanism}. A new singlet matter in addition to the right-handed
neutrinos is introduced to realize the double see-saw mechanism. The minimal
model gives an unambiguous Dirac neutrino mass matrix, which
enables us to predict the masses and the mixing angles in the enlarged neutrino mass matrix. Mixing angles between the light Majorana
neutrinos and the heavy sterile neutrinos are shown to be within the LEP
experimental bound on all ranges of the Majorana phases.Comment: 16 pages, 4 figures; the version to be published in Eur. Phys. J.
Nonlocal vortex motion in mesoscopic amorphous Nb0.7Ge0.3 structures
We study nonlocal vortex transport in mesoscopic amorphous Nb0.7Ge0.3
samples. A dc current I is passed through a wire connected via a perpendicular
channel, of a length L= 2-5 um, with a pair of voltage probes where a nonlocal
response Vnl ~ I is measured. The maximum of Rnl=Vnl/I for a given temperature
occurs at an L-independent magnetic field and is proportional to 1/L. The
results are interpreted in terms of the dissipative vortex motion along the
channel driven by a remote current, and can be understood in terms of a simple
model.Comment: 4 pages, 3 figure
Effects of hole-doping on the magnetic ground state and excitations in the edge-sharing CuO chains of CaYCuO
Neutron scattering experiments were performed on the undoped and hole-doped
CaYCuO, which consists of ferromagnetic edge-sharing
CuO chains. It was previously reported that in the undoped
CaYCuO there is an anomalous broadening of spin-wave
excitations along the chain, which is caused mainly by the antiferromagnetic
interchain interactions [Matsuda , Phys. Rev. B 63, 180403(R)
(2001)]. A systematic study of temperature and hole concentration dependencies
of the magnetic excitations shows that the magnetic excitations are softened
and broadened with increasing temperature or doping holes irrespective of
direction. The broadening is larger at higher . A characteristic feature is
that hole-doping is much more effective to broaden the excitations along the
chain. It is also suggested that the intrachain interaction does not change so
much with increasing temperature or doping although the anisotropic interaction
and the interchain interaction are reduced. In the spin-glass phase (=1.5)
and nearly disordered phase (=1.67) the magnetic excitations are much
broadened in energy and . It is suggested that the spin-glass phase
originates from the antiferromagnetic clusters, which are caused by the hole
disproportionation.Comment: 8 pages, submitted to Phys. Rev.
Neutrino Oscillations in a Supersymmetric SO(10) Model with Type-III See-Saw Mechanism
The neutrino oscillations are studied in the framework of the minimal
supersymmetric SO(10) model with Type-III see-saw mechanism by additionally
introducing a number of SO(10) singlet neutrinos. The light Majorana neutrino
mass matrix is given by a combination of those of the singlet neutrinos and the
active neutrinos. The minimal SO(10) model gives an unambiguous Dirac
neutrino mass matrix, which enables us to predict the masses and the other
parameters for the singlet neutrinos. These predicted masses take the values
accessible and testable by near future collider experiments under the
reasonable assumptions. More comprehensive calculations on these parameters are
also given.Comment: 14 pages, 5 figures; the version to appear in JHE
Distribution of partition function zeros of the model on the Bethe lattice
The distribution of partition function zeros is studied for the model
of spin glasses on the Bethe lattice. We find a relation between the
distribution of complex cavity fields and the density of zeros, which enables
us to obtain the density of zeros for the infinite system size by using the
cavity method. The phase boundaries thus derived from the location of the zeros
are consistent with the results of direct analytical calculations. This is the
first example in which the spin glass transition is related to the distribution
of zeros directly in the thermodynamical limit. We clarify how the spin glass
transition is characterized by the zeros of the partition function. It is also
shown that in the spin glass phase a continuous distribution of singularities
touches the axes of real field and temperature.Comment: 23 pages, 12 figure
Quasi-two-dimensional hole ordering and dimerized state in the CuO2-chain layers in Sr14Cu24O41
Neutron scattering experiments have been performed on
SrCuO which consists of both chains and ladders of copper
ions. We observed that the magnetic excitations from the CuO chain have two
branches and that both branches are weakly dispersive along the and
axes. The - dispersion relation as well as the intensities can be
reasonably described by a random phase approximation with intradimer coupling
between next-nearest-neighbor copper spins =11 meV, interdimer coupling
along the c axis =0.75 meV, and interdimer coupling along the a axis
=0.75 meV. The dimer configuration indicates a quasi-two-dimensional hole
ordering, resulting in an ordering of magnetic Cu with spin-1/2 and
nonmagnetic Cu, which forms the Zhang-Rice singlet. We have also studied the
effect of Ca substitution for Sr on the dimer and the hole ordering.Comment: 7 pages, Revtex, 10 figures, Submitted to Phys. Rev.
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